10 public questions tagged with this topic.
Propanal (CH₃CH₂CHO) is an aldehyde (positive Tollens' test) but lacks a CH₃C\=O group (negative iodoform test).
Ref: NCERT Class 12 Chemistry > Chapter 12: Aldehydes, Ketones and Carboxylic Acids > Topic: Nomenclature, Structure and Preparation of Aldehydes and Ketones
The iodoform test requires a CH₃C\=O group. Pentan-3-one (CH₃CH₂COCH₂CH₃) has no methyl ketone group, unlike the others.
Ref: NCERT Class 12 Chemistry > Chapter 12: Aldehydes, Ketones and Carboxylic Acids > Topic: Nomenclature, Structure and Preparation of Aldehydes and Ketones
The iodoform test is positive for compounds with a CH₃C\=O group, like acetophenone (C₆H₅COCH₃), but not for benzaldehyde (C₆H₅CHO).
Ref: NCERT Class 12 Chemistry > Chapter 12: Aldehydes, Ketones and Carboxylic Acids > Topic: Nomenclature, Structure and Preparation of Aldehydes and Ketones
Propan-1-ol (CH₃CH₂CH₂OH) oxidizes to propanal (CH₃CH₂CHO) with PCC, which lacks the CH₃CO- group and does not give an iodoform reaction.
Ref: NCERT Class 12 Chemistry > Chapter 7: Alcohols, Phenols and Ethers > Topic: Preparation of Phenols and Ethers - Williamson and Other Methods
Pentan-2-ol (CH₃CH(OH)CH₂CH₂CH₃) oxidizes to pentan-2-one (CH₃COCH₂CH₂CH₃), which has a CH₃CO- group and gives a positive iodoform test.
Ref: NCERT Class 12 Chemistry > Chapter 7: Alcohols, Phenols and Ethers > Topic: Preparation of Phenols and Ethers - Williamson and Other Methods
Ethanol (CH₃CH₂OH) oxidizes to acetaldehyde, which has a CH₃CO- group and gives a yellow iodoform precipitate with I₂ and NaOH.
Ref: NCERT Class 12 Chemistry > Chapter 7: Alcohols, Phenols and Ethers > Topic: Preparation of Alcohols - from Alkenes Haloalkanes Carbonyls Grignard
Butan-1-ol (CH₃CH₂CH₂CH₂OH) oxidizes to butanal, which lacks the CH₃CO- or CH₃CH(OH)- structure, giving a negative iodoform test.
Ref: NCERT Class 12 Chemistry > Chapter 7: Alcohols, Phenols and Ethers > Topic: Classification and Nomenclature and Structures of Alcohols Phenols Ethers
The iodoform test is positive for CH₃CH(OH)- structures. Propan-1-ol (CH₃CH₂CH₂OH) oxidizes to propanal, which lacks the required group, giving a negative result.
Ref: NCERT Class 12 Chemistry > Chapter 7: Alcohols, Phenols and Ethers > Topic: Classification and Nomenclature and Structures of Alcohols Phenols Ethers
The iodoform test is positive for alcohols with a CH₃CH(OH)- group. Propan-2-ol (CH₃CH(OH)CH₃) oxidizes to acetone, which gives a positive result.
Ref: NCERT Class 12 Chemistry > Chapter 7: Alcohols, Phenols and Ethers > Topic: Classification and Nomenclature and Structures of Alcohols Phenols Ethers
Ethanol (CH₃CH₂OH) oxidizes to acetaldehyde, which reacts with I₂ and NaOH in the iodoform test to form iodoform (CHI₃), a yellow precipitate.
Ref: NCERT Class 12 Chemistry > Chapter 7: Alcohols, Phenols and Ethers > Topic: Classification and Nomenclature and Structures of Alcohols Phenols Ethers
